JP2018180513A - Light source having monitoring function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source having a monitoring function that enables downsizing without requiring to further use a bulk component for monitoring optical output.SOLUTION: A light source having a monitoring function comprises: a plurality of laser diodes; a visible light coupler 310 using a planar light wave circuit; and at least one photo-diode. The visible light coupler comprises: a plurality of input waveguides that are optically connected to the plurality of laser diodes; a multiplexing unit 314 that multiplexes light output from the plurality of input waveguides; and an output waveguide 315 that outputs the light multiplexed in the multiplexing unit. At least one photo-diode is configured to monitor an optical output in the plurality of input waveguides, the multiplexing unit, or the output waveguide.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a light source with a monitoring function using a plurality of visible light sources such as red (R) light, green (G) light, and blue (B) light.

  In recent years, development of a compact RGB light source using a laser diode (LD) that outputs light of three primary colors of R (red light), G (green light) and B (blue light) for eyeglasses-type terminals and pico projectors It has been done. Since the LD has high straightness compared to the LED, a focus-free projector can be realized. In addition, LDs have high luminous efficiency, low power consumption, high color reproducibility, and have attracted attention in recent years.

  FIG. 1 shows a typical system outline of a projector using an LD. In the projector shown in FIG. 1, since the LDs 1 to 3 have single wavelength oscillation, the light of each color of R, G and B outputted from the LDs 1 to 3 is collimated using the lenses 4 to 6 respectively. The light is made incident on the dichroic mirrors 10 to 12 through the half mirrors 7 to 9, and a plurality of lights are bundled into one beam using the dichroic mirrors 10 to 12 and used as an RGB light source. The RGB light bundled and output in the dichroic mirrors 10 to 12 is swept using the MEMS mirror 16 or the like, synchronized with the modulation of the LD, and an image is output and projected on the screen 17.

  At this time, in order to adjust the white balance, a part of each light collimated using the lenses 4 to 6 is branched by the half mirrors 7 to 9 and made to enter the photodiodes (PD) 13 to 15 to be PD 13 to 15 Monitor the output by Therefore, as shown in FIG. 1, for use as an RGB light source, bulk components such as LD 1 to 3, lenses 4 to 6, half mirrors 7 to 9, dichroic mirrors 10 to 12 and PDs 13 It is necessary to combine according to the system. Here, although the LD emits light in the front and back direction, the front side (front monitoring) is general because the accuracy in the rear side monitoring is poor.

  Furthermore, since R and G have a weak output of LD compared to B, RRGGB light source etc. which combined R and G two by two may be used.

A. Nakao, R. Morimoto, Y. Kato, Y. Kakinoki, K. Ogawa and T. Katsuyama, “Integrated waveguide-type red-green-blue beam combiners for compact projection-type displays”, Optics Communications 330 (2014) 45-48 Y. Hibino, "Arrayed-Waveguide-Grating Multi / Demultiplexers for Photonic Networks," IEEE CIRCUITS & DEVICES, Nov., 2000, pp. 21-27 A. Himeno, et al., “Silica-Based Planar Lightwave Circuits,” J. Sel. Top. Q. E., vol. 4, 1998, pp. 913-924 J. Sakamoto et al. “High-efficiency multiple-light-source red-green-blue power combiner with optical waveguide mode coupling technique,” Proc. Of SPIE Vol. 10126 101260M-2

  However, when combining the light of each wavelength of the RGB light source using a space optical system, bulk components such as a half mirror and a dichroic mirror are additionally required to monitor the light output for adjusting the white balance. Since the size of the system is increased, there is a problem in that the miniaturization of the light source is hindered.

  A light source with a monitoring function according to an aspect of the present invention is a visible light coupler using a planar light wave circuit that combines a plurality of laser diodes and light output from the plurality of laser diodes and outputs the combined light. And at least one photodiode, the visible light coupler combining a plurality of input waveguides optically connected to the plurality of laser diodes with light output from the plurality of input waveguides. And at least one photodiode includes the plurality of input waveguides, the combining unit, or the output. The at least one photodiode may include a combining unit that generates waves and an output waveguide that outputs the light combined in the combining unit. It is characterized in that it is configured to monitor the light output in the waveguide.

  According to the light source with a monitoring function according to the present invention, it is possible to create a multiplexer by PLC without devising bulk parts such as a half mirror or a dichroic mirror for monitoring light output, and devise a layout of PLC Since the light output can be monitored simply by providing the PD, the RGB light source can be miniaturized.

It is a figure which shows the typical system outline of the projector which used LD. It is a figure which shows the basic structure of the RGB coupler which used PLC. It is a figure which shows the structure of a RGB coupler using two directional couplers. It is a figure which shows the structure of RRGGB coupler using a mode coupler. FIG. 5 is a view showing the relationship between the effective refractive index of light of zeroth order, first order, and second order mode for each wavelength and the waveguide width in the RGB coupler 210 using the mode coupler shown in FIG. 4. It is a figure which shows the light source with a monitoring function which concerns on Example 1 of this invention. It is a figure which shows the other example of the light source with a monitoring function which concerns on Example 1 of this invention. It is a figure which shows the further another example of the light source with a monitoring function which concerns on Example 1 of this invention. It is a figure which shows the light source with a monitoring function which concerns on Example 2 of this invention. It is a figure which shows the other example of the light source with a monitoring function which concerns on Example 2 of this invention. It is a figure which shows the further another example of the light source with a monitoring function which concerns on Example 2 of this invention. It is a figure which shows the further another example of the light source with a monitoring function which concerns on Example 2 of this invention. It is a figure which shows the light source with a monitoring function which concerns on Example 3 of this invention. It is a figure which shows the light source with a monitoring function which concerns on Example 4 of this invention. It is a figure which shows the light source with a monitoring function which concerns on Example 6 of this invention. It is a figure which shows the light source with a monitoring function which concerns on Example 7 of this invention. It is a figure for demonstrating the light source with a monitoring function which concerns on Example 8 of this invention.

(Reference example)
An RGB coupler module using a silica-based planar lightwave circuit (PLC) will be described below with reference to FIGS. 2 to 5 in order to understand the embodiments described later.

  In recent years, an RGB coupler module using PLC instead of RGB multiplexing by bulk components as shown in FIG. 1 has attracted attention (see, for example, Non-Patent Document 1). The PLC manufactures an optical waveguide on a planar substrate such as Si by patterning by photolithography and reactive ion etching, and a plurality of basic optical circuits (for example, directional coupler, Mach-Zehnder interferometer, etc.) Various functions can be realized by combining (see, for example, Non-Patent Documents 2 and 3).

  FIG. 2 shows the basic structure of an RGB coupler using a PLC. FIG. 2 shows an RGB coupler module including first to third LDs 21 to 23 and a PLC type RGB coupler 30. The RGB coupler 30 includes first to third waveguides 31 to 33, and symmetrical first and second directional couplers 34 and 35 having the same waveguide width. As shown in FIG. 2, the RGB coupler 30 has a waveguide structure having three input ports and one output port.

  As a multiplexing method in the RGB coupler module using PLC, a method using two symmetrical directional couplers having the same waveguide width, a method using a Mach-Zehnder interferometer (see, for example, non-patent document 1), a mode coupler There is a method (see, for example, Non-Patent Document 4) that uses By using the PLC, the RGB multiplexing optical system realized using a lens, a dichroic mirror or the like can be integrated on one chip. Further, as shown in Non-Patent Document 2, a method is also reported in which light of the same wavelength is multiplexed in different modes using mode multiplexing to realize an RRGGB coupler.

  An RGB coupler using two directional couplers will be described with reference to FIG. In FIG. 3, output waveguides 106 connected to first to third input waveguides 101 to 103, first and second directional couplers 104 and 105, and second input waveguide 102. An optical multiplexing circuit is provided.

  In the optical multiplexing circuit shown in FIG. 3, for example, the first input waveguide 101 is blue light B (wavelength λ1), the second input waveguide 102 is green light G (wavelength λ2), and the third input waveguide A red light R (wavelength λ3) 103 is input to the light source 103. The three color lights R, G, and B are combined by the first and second directional couplers 104 and 105 and output from the output waveguide 106.

  The first directional coupler 104 couples the light of λ 1 incident from the first input waveguide 101 to the second input waveguide 102, and the light of λ 2 incident from the second input waveguide 102. The waveguide length, waveguide width and gap between the waveguides are designed to couple to the first input waveguide 101 and to couple back to the second input waveguide 102. The second directional coupler 105 couples the light of λ 3 incident from the third input waveguide 103 to the second input waveguide 102, and the second directional coupler 104 The waveguide length, the waveguide width and the gap between the waveguides are designed to transmit the light of λ 1 and λ 2 coupled to the waveguide 102.

  As described above, in the optical multiplexing circuit shown in FIG. 3, light of three wavelengths λ1 to λ3 is multiplexed and emitted from the output waveguide 106. For example, light of 450 nm, 520 nm, and 638 nm is used as light of λ1, λ2, and λ3, respectively.

  Subsequently, an RRGGB coupler using a mode coupler will be described with reference to FIG. In FIG. 4, first to fifth input waveguides 211 to 215, first and second directional couplers 231 and 232 having the same waveguide width, and third and fourth waveguides having different waveguide widths are illustrated. And optical couplers 233 and 234, respectively.

As shown in FIG. 4, the third input waveguide 213 is configured with a tapered waveguide structure so as to have _first and _second portions 2131 and 2132 having different waveguide widths. Also, the first, second, fourth and fifth input waveguides 211, 212, 214 and 215 are single mode waveguides, and the third input waveguide 213 is a multimode waveguide.

  For example, green light G2 and G1, blue light B, and red light R1 and R2 are incident on the first to fifth input waveguides 211 to 215, respectively. For example, light B, G1, and R1 are light having wavelengths in the wavelength range of 400 to 495 nm, 495 to 570 nm, and 620 to 750 nm, respectively, and G2 and R2 have wavelengths of 495 to 570 + β nm and 620 to 750 + γ nm, respectively. .Beta. And .gamma. Are small values of 0 or more and the line width or less, and the line width can be approximately 1 nm or less depending on the light source of the incident light.

  The first directional coupler 231 couples the light G1 incident from the second input waveguide 212 to the third input waveguide 213, and the light B incident from the third input waveguide 213 The waveguide length, waveguide width and gap between the waveguides are designed to couple to the two input waveguides 212 and couple back to the third input waveguide 213.

  The second directional coupler 232 couples the light R1 incident from the fourth input waveguide 214 to the third input waveguide 213, and the third directional waveguide 231 is configured to receive the third input waveguide. The waveguide length, the waveguide width, and the gap between the waveguides are designed to transmit the lights G1 and B coupled to the light source 213.

Third directional coupler 233 is disposed on the first portion 213 ₁ near the third input waveguide 213. Fourth directional coupler 234 is arranged in the second portion 213 ₂ near the third input waveguide 213.

  The third and fourth directional couplers 233 and 234 are mode couplers configured by asymmetric directional couplers having different waveguide widths (see, for example, Non-Patent Document 4). In the mode coupler, the effective refractive index of the light of the zero-order mode in the narrow waveguide with the narrower waveguide width matches the effective refractive index of the light of the high-order mode in the wider waveguide with the wider waveguide width. At the same time, the light of the zero-order mode propagating through the narrow waveguide can be 100% coupled to the adjacent wide waveguide while being converted to the light of the high-order mode. On the other hand, the zeroth-order mode light propagating through the wide waveguide is never coupled to the adjacent narrow waveguide because the effective refractive index of the zero-order mode light in the narrow waveguide does not match. Pass through the mode coupler.

In order to function as a mode coupler, the third directional coupler 233 sets the effective refractive index in the zero-order mode of the light G 2 for the first input waveguide 211 and the first portion 213 of the third input waveguide 213. so that the effective refractive index equal at the high-order mode light G2 for _1, and the effective refractive index in the higher order modes of light G1, B, R1 to the first portion 213 ₁ of the third input waveguide 213 When light G1 for the first input waveguide 211, B, so that the effective refractive index not equal in R1 0-order mode, the first input waveguide 211 and first portion 213 ₁ of the waveguide width is set It is done.

Similarly, in order to function as a mode coupler, the fourth directional coupler 234 is configured to set the effective refractive index in the zero-order mode of the light R2 to the fifth input waveguide 215 and the second refractive index of the third input waveguide 213. so that the effective refractive index becomes equal with respect to the portion 213 ₂ of the higher order modes of light R2, and, in the higher order modes of light G1, B, R1 to the second portion 213 ₂ of the third input waveguide 213 The waveguides of the fifth input waveguide 215 and the second portion 213 ₂ so that the effective refractive index and the effective refractive index in the zeroth mode of the light G 1, B, R 1 for the fifth input waveguide 215 are not equal. The width is set.

  The operation of the optical multiplexing circuit shown in FIG. 4 will be described. The zero-order mode light G1 incident from the second input waveguide 212 is coupled to the third input waveguide 213 in the first directional coupler 231 having the same waveguide width, and the third input waveguide The zero-order mode light B incident from the waveguide 213 is coupled to the second input waveguide 212 at the first directional coupler 231 and coupled again to the third input waveguide 213.

The zero-order mode light R1 incident from the fourth input waveguide 214 is coupled to the third input waveguide 213 in the second directional coupler 232 having the same waveguide width, and the third input waveguide The lights G 1 and B propagating through the waveguide 213 are transmitted by the second directional coupler 232. As a result, the lights G1, B, R1 incident on the first to third input waveguides 211 to 213 are multiplexed through the first and second directional couplers 231 and 232, and the third light is input to the first portion 213 ₁ of the input waveguide 213.

On the other hand, the zeroth-order mode light G2 propagating in the first input waveguide 211 is converted into a higher-order mode by the third directional coupler 233 functioning as a mode coupler, and the third directional coupler 233 Coupled to the first portion 213 ₁ of the input waveguide 213. Light G2 of bound higher-order mode, is the third input light G1 of the first order mode of a part 213 ₁ propagating in the waveguide 213, B, R1 and multiplexing, the third input guide is input to the second portion 213 ₂ of the waveguide 213.

Furthermore, the zeroth-order mode light R2 propagating through the fifth input waveguide 215 is converted to a higher-order mode by the fourth directional coupler 234 functioning as a mode coupler, and the third directional coupler 234 coupled to second portion 213 ₂ of the input waveguide 213. Light R2 of bound higher-order mode is further combined with the third of the second portion 213 ₂ and the propagated are multiplexed optical input waveguide 213. As a result, the combined light of the lights G 2, G 1, B, R 1 and R 2 incident to the first to fifth input waveguides 211 to 215 is output from the output port of the third input waveguide 213 to the space modulation optical element 220. It is output.

  FIG. 5 shows the effective refractive index and the conductivity of light of the 0th, 1st and 2nd modes for each wavelength λ 1 = 450 nm, λ 2 = 520 nm, λ 3 = 650 nm in the RGB coupler 210 using the mode coupler shown in FIG. The relationship with the waveguide width is shown. The waveguide film thickness was 3.6 μm, and the relative refractive index difference Δ was 0.45%.

For example, the gap between the waveguides in the first directional coupler 231 is 2 μm, the gap between the waveguides in the second directional coupler 232 is 4.7 μm, and the first input waveguide 211 and the first portion 213 ₁ When the fifth input waveguide 215 and a second portion 213 ₂ and each gap between the waveguides in the 2.5 [mu] m, 3000 .mu.m a coupling length of the first and second directional couplers 231 and 232, third The coupling length of the directional coupler 233 is 2380 μm, the coupling length of the fourth directional coupler 234 is 900 μm, and the waveguide width of the first and fifth input waveguides 211 and 215 is 1.5 μm. The waveguide width of the fourth through fourth input waveguides 212 and 214 is assumed to be 2 μm. In this case, based on FIG. 5, for each wavelength λ1 to λ3 Considering the waveguide width effective refractive index becomes equal, the first portion 213 ₁ of the waveguide width 7.15Myuemu, the second portion 213 ₂ By setting the waveguide width to 8.00 μm, it can be seen that an RGB coupler 210 using a mode coupler as shown in FIG. 4 can be realized.

  Hereinafter, each example of the present invention will be described. In the present specification, an embodiment is described using a specific multiplexing method, but the present invention is not limited by the multiplexing method.

Example 1
A light source with a monitoring function according to the first embodiment of the present invention will be described using FIGS. 6 to 8. FIG. 6 shows a light source with a monitoring function according to Embodiment 1 of the present invention. Figure 6 is, R, G, and first to third LD301 ₁ to 301 ₃ respectively output colors of the light of B, the the RGB coupler 310 of the PLC type, which is optically connected to the RGB coupler 310 A light source with a monitoring function comprising the _{first to} third PDs 302 _{1 to} 302 ₃ is shown.

As shown in FIG. 6, RGB coupler 310 of the PLC type, the first to third LD301 ₁ to 301 ₃ and the first to third input waveguide 311 ₁ to 311 ₃ that is optically connected, the first to third branching unit 312 ₁ to 312 ₃ to 2 branches the light propagating in the waveguide, the first through third light branched respectively bifurcation 312 ₁ to 312 ₃ of the first to third the PD 302 ₁ to 302 ₃ first to third monitoring waveguide 313 ₁ to 313 ₃ and outputs to a multiplexing section 314 for multiplexing the input light, the combined by the combining unit 314 light And an output waveguide 315 for output.

In RGB coupler 310 of the PLC type shown in FIG. 6, the light incident to the first to third input waveguide 311 ₁ to 311 ₃ are each bifurcated in the first to third branching unit 312 ₁ to 312 ₃ Be done. One of the branched light is output to the first to third PD 302 ₁ to 302 ₃ through the first to third monitoring waveguide 313 ₁ to 313 _3, and the other of the split optical Expediently The waves are combined in the wave section 314 and output to the output waveguide 315.

For example, an optical multiplexing circuit using a directional coupler as shown in FIG. 3 can be used as the multiplexing unit 314 (the same applies to the following embodiments). In this case, the first to third input waveguide 311 ₁ to 311 _3, respectively, coupled to the first to third input waveguide 101 through 103 shown in FIG. 3, the output waveguide 315, in FIG. 3 Coupled to the output waveguide 106 shown. However, the present invention is not limited to this, and another waveguiding unit (for example, a Mach-Zehnder interferometer or the like) may be used as the multiplexing unit 314 (the same applies to the following embodiments).

As shown in FIG. 6, when the branching each light propagating through the first to third input waveguide 311 ₁ through 311 ₃ in the first to third branching unit 312 ₁ to 312 _3, first through third with an LD301 ₁ to 301 ₃ can monitor the binding characteristics of the first to third input waveguide 311 ₁ to 311 _3, and by the measurement for the pre-characteristic of the multiplexing unit 314 grasped, It is possible to adjust the white balance using monitoring values.

  FIG. 7 shows another example of a light source with a monitoring function according to the first embodiment of the present invention. In the example illustrated in FIG. 7, the branching unit 312 is provided in the vicinity of the multiplexing unit 314, and the light that is not multiplexed or is leaked in the multiplexing unit 314 is output from the discard port to which the light is output. The mixed light of each color is branched by the branching unit 312 and is input to the PD 302.

  Taking the optical multiplexing circuit shown in FIG. 3 as the multiplexing section 314 as an example, the second directional coupler 105 which is the directional coupler closest to the output side is used as the branching section 312 and is not coupled to the output port Among the input waveguides, it is preferable to use the third input waveguide 103 closest to the output side as it is as the monitoring waveguide 313 by connecting it to the PD 302 as it is. In addition, the third input waveguide 103 that is near the second directional coupler 105 that is the directional coupler closest to the output side, or the input waveguide that is not coupled to the output port, is the closest to the output side. The bifurcated portion 312 may be provided in the vicinity of the tip portion of the.

  As shown in FIG. 7, in the case where light propagating in the multiplexing unit 314 is branched by the branching unit 312, light in which each color of R, G, and B is mixed is input to the PD 302 using the discard port of the multiplexing unit 314. In order to perform monitoring without preparing a monitoring circuit for each of R, G, and B, a smaller light source can be realized, and measurement for grasping the characteristics of the multiplexer 314 in advance is performed. It is possible to adjust the white balance using the monitoring values.

  FIG. 8 shows still another example of the light source with a monitoring function according to the first embodiment of the present invention. In the example shown in FIG. 8, the branch portion 312 is provided in the vicinity of the output waveguide 315, and the coupled light propagating through the output waveguide 315 is branched by the branch portion 312 and is input to the PD 302.

  As shown in FIG. 8, when the light propagating through the output waveguide 315 is branched at the branch portion 312, the output of the output waveguide 315 can be directly monitored, and monitoring is not performed without preparing a monitoring circuit for each color. As a result, a smaller light source can be realized, and the white balance can be adjusted without grasping the multiplexing characteristic of the multiplexing unit 314 in advance.

  In the first embodiment, the case where the light source is one for each of R, G, and B is described, but even when five light sources such as RRGGB are used, the light combining circuit shown in FIG. It goes without saying that monitoring is likewise possible by using the additional PD 302, the branching portion 312 and the monitoring waveguide 313. The same applies to the following embodiments.

  The branch unit 312 can branch light for monitoring by using a circuit capable of branching light propagating through the waveguide, such as a directional coupler or a Y-branch waveguide. As shown in FIGS. 6 to 8, the light may be branched from any of the input waveguide 311, the coupler 314, and the output waveguide 315. In either case, additional components such as a half mirror are unnecessary, and there is no increase in size due to the addition of an optical path, so the light source module can be miniaturized.

(Example 2)
A light source with a monitoring function according to a second embodiment of the present invention will be described using FIGS. 9 to 12. 9 to 12 show an example of a light source with a monitoring function according to a second embodiment of the present invention. The 9 to 12, R, G, and first to third LD401 ₁ to 401 ₃ respectively output colors of the light of B, the RGB coupler 410 of the PLC type, optically connected to the RGB coupler 410 And a monitoring light source with the illustrated PD 402.

As shown in FIGS. 9 to 12, RGB coupler 410 of the PLC type, the first to third LD401 ₁ to 401 ₃ and the first to third optically connected to the input waveguide 411 ₁ to 411 ₃ , a branching unit 412 for branching the light propagating through the waveguide into two, a monitoring waveguide 413 for outputting the light branched by the branching unit 412 to the PD 402, and a multiplexing unit 414 for multiplexing the input light And an output waveguide 415 that outputs the light combined in the combining unit 414.

  In the second embodiment, the positional relationship between LD and PD will be described. If the PD 402 is disposed to face the exit surface of the LD 401 as in the first embodiment, stray light may be incident on the PD 402 and an accurate value may not be obtained.

In a second embodiment, as LD401 and PD402 does not face, by using a bending waveguide for optical path conversion 90 °, first to third LD401 ₁ to 401 of the light in the _three outgoing direction PD402 The stray light can be prevented from entering the PD by being configured to be substantially perpendicular to the incident direction of the light at the point.

For example, by using a bending waveguide for optical path conversion 90 ° as monitoring waveguide 413 in the example shown in FIG. 9, also, the first to third input waveguide 411 ₁ through 411 in the example shown in FIG. 10 by using the 90 ° bend waveguides for optical path conversion as _3, configured as light emitting direction in the first to third LD401 ₁ to 401 ₃ is approximate perpendicular to the incident direction of light in the PD402 It is done.

  On the other hand, bending the waveguide requires a long circuit length, and the module becomes larger. In addition, since the light R, G, B travels in a broad band with a wavelength of 450 to 650 nm, the minimum bending radius that can bend the waveguide without loss differs depending on the color. In particular, light R, which has a large penetration of light, has a larger minimum bending radius than light G and light B. For example, in the case of a waveguide having a refractive index difference of 0.45% and a waveguide width of about 3.5 μm, the minimum bending radius of the waveguide for propagating the lights G and B is 1 to 2 mm, The minimum bending radius of the waveguide propagating through is approximately 5 mm.

Therefore, as shown in FIG. 11, in order to bend the input waveguide 411 ₁ for propagating light R unnecessary, as LD401 ₁ of the exit surface for outputting light R faces the incident surface of the PD402 LD401 ₁ the arrangement to form an input waveguide 411 ₁ and output waveguides 415 as a linear waveguide, as the exit surface of the light G and outputs the B LD401 ₂ and 401 ₃ is orthogonal to the LD401 ₁ exit surface the input waveguide 411 ₂ and 411 ₃ for propagating light G and B constructed by bending so as to convert 90 ° optical path arranged to further so as not to come on the center line of the LD401 ₁ of the exit surface for outputting light R The PD 402 was placed on the As a result, it is possible to realize a compact light source with a monitoring function in which stray light does not easily enter.

Alternatively, in the example shown in FIG. 12, as the LD401 ₁ to 401 ₃ and PD402 does not face, reducing the incidence of stray light on the PD402 by using a bending waveguide of 90 ° optical path conversion as monitored waveguide 413 in addition to that by the LD401 ₁ to 401 ₃ provided on surface facing the emission surface for outputting the output light, the input waveguide 411 ₃ and the output waveguides 415 that propagates light R and the straight waveguide, the input waveguide 411 ₁ and 411 ₂ for propagating light B and G respectively as bending waveguide for optical path conversion, are connected to the respective multiplexing unit 414. Further, LD401 ₃ that outputs light R is three arranged on the most end of the LD401 ₁ to 401 _3, are arranged farthest from the PD402 in and the input waveguide 411 _{in three} directions parallel to the plane of incidence of There is.

As a result, the length of the chip can be minimized while the bending region of the waveguide is brought close to one side in the width direction of the RGB coupler 410, so that downsizing of the light source with a monitoring function can be realized. Furthermore, in the configuration shown in FIG. 12, by not arranging the exit surface of the LD401 ₁ to 401 ₃ output on the center line of the exit surface waveguide 415, it reduces the stray light is incident on the exit surface of the output waveguide 415 It is possible to

  In the configurations shown in FIG. 11 and FIG. 12, the arrangement of the LDs 401 that output the lights R, B and G may be interchanged.

(Example 3)
A light source with a monitoring function according to a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a cross-sectional view of a light source with a monitoring function according to a third embodiment of the present invention. As shown in FIG. 13, at the output end of the monitoring waveguide 513, a flip-up mirror 501 is provided which converts the optical path of the incident light by 90 °. Also, the PD 502 is arranged to be optically connected to the light whose optical path is changed by the bounce mirror 501.

  In this embodiment, the PD 502 is mounted on the surface of the PLC, and the light emitted from the monitoring waveguide 513 is reflected above the substrate by using the flip-up mirror 501 to be incident on the PD 502. The flip-up mirror 501 is a method of affixing a surface having a 45 ° inclination prepared separately using Si or the like to the output end face of the monitoring waveguide 513, or a substrate is inclined at 45 ° for dry etching. It can be manufactured by a method of forming in the middle of the waveguide 513.

  According to this embodiment, since the PD 502 can be disposed so as not to face the emission surface of the LD, stray light is not easily incident on the PD, and there is no need to bend the waveguide, so a compact light source with a monitoring function can be realized. .

(Example 4)
FIG. 14 illustrates a light source with a monitoring function according to a fourth embodiment of the present invention. Figure 14, G2, and G1, B, R1, first to fifth LD 601 ₁ to 601 ₅ respectively output light R2, the RGB coupler 610 of the PLC type, is optically connected to the RGB coupler 610 first to third PD602 ₁ to 602 _3, the monitoring function light source with a shown a.

As shown in FIG. 14, RGB coupler 610 of the PLC type, the input waveguide 611 ₁ to 611 ₅ of the first to the first to fifth connected fifth LD 601 ₁ to 601 ₅ and optically, the light propagating in the waveguide and the first to fifth branch portion 612 ₁ to 612 ₅ to 2 branches, the first to fifth light branched respectively bifurcation 612 ₁ to 612 ₅ of the first to third the first to fifth monitoring waveguide 613 ₁ to 613 ₅ and outputs the PD602 ₁ to 602 _3, and the combining part 614 for multiplexing the input light, the combined by the combining unit 614 light And an output waveguide 615 for output.

As shown in FIG. 14, in the light source with a monitoring function according to the fourth embodiment, light G2 and G1 of the same color output from the _first and _second LDs 6011 and 6012 respectively have first and second branches. the first is input to the PD602 ₁ through the parts 612 ₁ and 612 _2, light B which third LD 601 ₃ outputs is inputted third branch portion 612 ₃ to the second PD602 ₂ via a first fourth and fifth LD 601 ₄ and 601 ₅ are light R1 and R2 of the same color to be output is input to the third PD602 ₃ via the branching unit 612 _4, 612 ₅ of the fourth and fifth, respectively.

  Conventionally, monitoring was performed by arranging one PD corresponding to each LD, but as shown in FIG. 14, monitoring optically connected via an LD 601 that outputs light of the same color via a branch unit 612 The optical waveguide 613 is connected to the same PD 602, and light of the same color is incident on the same PD 602 for each of R, G and B, thereby reducing the number of PDs and further downsizing It is possible to monitor the light power of each color necessary for white balance adjustment while

(Example 5)
A light source with a monitoring function according to a fifth embodiment of the present invention will be described with reference to FIGS. 7 and 8. In the configuration in which the branching unit 312 is provided in the vicinity of the multiplexing unit 314 and the output waveguide 315 as illustrated in FIGS. 7 and 8, light in which the colors are mixed is input to the PD 302. Therefore, in order to accurately monitor the light power of each color, it is necessary to separate the light of each color.

The monitoring function light source according to Embodiment 5, by time division or frequency modulation of the first to third LD301 ₁ to 301 ₃ output optical electric signal processing each color each time the signals from the same PD302 upon It is possible to separate

For example, the modulation frequencies f _LD of the _{first to third LDs} 301 _{1 to} 301 ₃ necessary for video output are determined by the following (Expression 1).
f _LD = (number of pixels) × (frame rate) ÷ (rate of blanking time) (Equation 1)

In general, the frame rate is 60 Hz, the blanking time ratio (ratio of time during which the LD does not emit light) is 0.5, and the number of pixels is approximately 153600 to 1382400. Therefore, the first to third LD 301 ₁ the to 301 _3, the modulation of about 18.4~165.9MHz are required for video output.

If time division modulating a first to third LD301 ₁ to 301 ₃ of the output light, so as not to affect the image, so that at least the frame rate is higher than 60 Hz, the first to third LD301 ₁ time division modulating the 301 _third output light can be monitored output light for each color. In this case, it is preferable to sequentially emit one LD of the first to third LD301 ₁ to 301 ₃ during unrelated blanking time video.

When frequency-modulating the output light of the _{first to} third LDs 301 _{1 to} 301 ₃ , the frequency is sufficiently higher (for example, several hundreds MHz to several GHz) than the modulation frequency required for video output, and red light and blue light Alternatively, monitoring the output light of each color without affecting the image by frequency modulating the output light of the _{first to} third LDs 301 _{1 to} 301 ₃ using different frequencies for each LD 301 that outputs green light It is possible to

  As a result, it is possible to realize a compact light source with a monitoring function by reducing the number of PDs while enabling monitoring of light of each color.

  In addition, in the LD, reflected light interferes due to the high coherence of the LD, and speckles in which an image is flickering are generated. When the above-described frequency modulation is added to the output of the LD 301, the coherence is reduced in a pseudo manner, and an effect of speckle reduction can also be obtained.

(Example 6)
FIG. 15 shows a light source with a monitoring function according to a sixth embodiment of the present invention. Figure to 15, R, G, and first to third LD701 ₁ to 701 ₃ respectively output colors of the light of B, the RGB coupler 710 of the PLC type, the first to third LD701 ₁ to 701 ₃ first to third PD702 ₁ to 702 ₃ respectively arranged in the connection portion upper surface, monitoring function light source with the shown with RGB coupler 710 and.

As shown in FIG. 15, RGB coupler 310 of the PLC type, the first to third LD701 ₁ to 701 ₃ and the first to third input waveguide 711 ₁ to 711 ₃ that is optically connected, first to include a multiplexer 714 for multiplexing the light input from the third input waveguide 711 ₁ to 711 _3, and the output waveguides 715 for outputting the multiplexed by multiplexing section 714 light.

In the above embodiment, the branch portion is branched light using has been monitored through the monitoring waveguide the branched light, in this embodiment, first to third LD701 ₁ to 701 ₃ and RGB coupler 710 connecting the vicinity (e.g., the connecting portion upward) of the first to third PD702 ₁ to 702 ₃ respectively arranged in, for monitoring the leakage light became splice loss.

First to third LD701 ₁ to 701 ₃ first to third input waveguide 711 ₁ to 711 _3, depending on the structure, since the mode field are different, connection loss 1~2dB occurs. Light which has not been connected to the first to third LD701 ₁ to 701 ₃ first to third is emitted from the input waveguide 711 ₁ to 711 _3, in order to scatter near the connecting portion, first to 3 of LD701 ₁ to 701 ₃ and the first to third input waveguide 711 ₁ to 711 ₃ and the first to third connection portions vicinity of PD702 ₁ to 702 ₃ by placing each output of the light source It becomes possible to monitor.

  According to the present embodiment, it is not necessary to prepare a branch portion and a monitoring waveguide, so that a compact monitoring light source can be realized.

(Example 7)
FIG. 16 illustrates the configuration of a light source with a monitoring function according to a seventh embodiment of the present invention. Figure 16 is, R, G, and first to third LD801 ₁ to 801 ₃ respectively output colors of the light of B, the RGB coupler 810 of the PLC type, which is optically connected to the RGB coupler 810 PD802 And a monitoring equipped light source is shown.

As shown in FIG. 16, RGB coupler 810 of the PLC type, the first to third LD801 ₁ to 801 ₃ and the first to third input waveguide 811 ₁ to 811 ₃ that are optically connected, the 1 to multiplexing section 814 that multiplexes the light input from the third input waveguide 811 ₁ to 811 _3, and the output waveguides 815 for outputting the multiplexed by multiplexing section 814 optical output waveguides 815 And a monitoring waveguide 813 for propagating the light reflected by the reflection unit 817 and outputting the light to the PD 802.

  The output waveguide 815 is provided with a bending portion 816 so that the output light is emitted while being inclined with respect to the output surface of the output light. A reflection portion 817 is provided at the connection portion between the monitoring waveguide 813 and the output waveguide 815, and the reflection portion 817 reflects the HR coat 818 for reflecting the desired ratio of the output light on the emission surface of the output waveguide 815. It is constituted by giving.

  The combined light output from the combining unit 814 is inclined with respect to the output surface of the output light at the bending unit 816 and enters the reflecting unit 817 on which the HR coat 818 is applied, and is reflected at a desired ratio at the reflecting unit 817 Be done. The light reflected by the reflection unit 817 propagates through the monitoring waveguide 813 as monitoring light and enters the PD 802, and the light transmitted through the reflection unit 817 is output as output light.

  According to the seventh embodiment, there is no need to prepare a branch portion and a bending waveguide for 90 ° optical path conversion, so a small monitoring light source can be realized.

(Example 8)
Eighth Embodiment A light source with a monitoring function according to an eighth embodiment of the present invention will be described with reference to FIG. FIG. 17 (a) illustrates the configuration of the emission surface of the waveguide in the light source with a monitoring function according to Embodiment 8 of the present invention, and FIG. 17 (b) illustrates the configuration of the emission surface of the waveguide in a conventional light source with a monitoring function. To illustrate. As shown in FIG. 17 (b), in the waveguide in the conventional light source with a monitoring function, the waveguide is provided until reaching the emission surface.

  It is known that visible laser light collects organic substances and the like in the atmosphere if the energy density at the exit surface of the waveguide is high. Since the outgoing beam has a Gaussian shape, the collected organic matter has a lens shape, and there is a problem that the outgoing beam shape is deformed.

  Therefore, in the light source with a monitoring function according to the eighth embodiment, as shown in FIG. 17A, the output waveguide and / or the monitoring waveguide are terminated before reaching the exit surface. By doing so, the energy density of light at the end face (waveguide exit end) of the RGB coupler can be reduced, and a good exit beam shape can be obtained. Furthermore, due to the reduction of the energy density of light at the waveguide output end, the light reflected at the end face is hardly recombined with the waveguide, and the energy density of stray light entering the chip without entering the waveguide is reduced. It is possible to reduce the incidence of stray light on the PD.

  The configurations according to the first to eighth embodiments can be appropriately combined and applied without departing from the principle and concept of the present invention.

Claims (12)

With multiple laser diodes,
A visible light coupler using a planar lightwave circuit, which multiplexes the light output from the plurality of laser diodes and outputs the combined light.
At least one photodiode,
Including
The visible light coupler is
A plurality of input waveguides optically connected to the plurality of laser diodes;
A multiplexing unit that multiplexes the light output from the plurality of input waveguides;
And an output waveguide for outputting the light combined in the combining unit,
A light source with a monitoring function, wherein the at least one photodiode is configured to monitor a light output in the plurality of input waveguides, the combining unit, or the output waveguide. The visible light coupler is
At least one branch for branching light propagating in the waveguide;
At least one monitoring waveguide that propagates the light branched by the at least one branch and outputs the light to the at least one photodiode;
Further include
The light source with a monitoring function according to claim 1, wherein the at least one branch portion is provided in the vicinity of the plurality of input waveguides, the combining portion, or the output waveguide.   The light source with a monitoring function according to claim 2, wherein the plurality of input waveguides or the at least one monitoring waveguide are bending waveguides for 90 ° optical path conversion. Among the plurality of input waveguides, the input waveguide connected to a laser diode that outputs red light is a linear waveguide,
Among the plurality of input waveguides, the input waveguide excluding the input waveguide connected to the laser diode that outputs the red light is a bending waveguide for light path conversion,
The light source with a monitoring function according to claim 2, wherein the at least one photodiode is not disposed on the center line of the emission surface of the laser diode that outputs the red light. Among the plurality of input waveguides, an input waveguide connected to a laser diode that outputs red light and the output waveguide are linear waveguides,
The at least one monitoring waveguide is a bending waveguide for 90 ° path conversion,
Among the plurality of input waveguides, the input waveguide excluding the input waveguide connected to the laser diode that outputs the red light is a bending waveguide for light path conversion,
The laser diode that outputs the red light is disposed at the extreme end of the plurality of laser diodes, and is disposed at the farthest position from the at least one photodiode in a direction parallel to the incident plane of the plurality of input waveguides. And
The light source with a monitoring function according to claim 2, wherein the emission surface of the output waveguide is not disposed on the center line of the emission surface of the laser diode that outputs the red light.   The light source with a monitoring function according to any one of claims 2 to 5, wherein the output waveguide and / or the at least one monitoring waveguide are terminated before reaching an exit surface. It further comprises a bounce mirror provided on the way or at the output end of the monitoring waveguide, for converting the optical path of the incident light,
The light source with a monitoring function according to any one of claims 2 to 6, wherein the at least one photodiode is disposed to receive the light whose optical path is converted. The branch portion is provided in the vicinity of each of the plurality of input waveguides,
The set of the monitoring waveguides optically connected to the laser diode outputting the light of the same color via the branch portion is optically connected to the same photodiode. A light source with a monitoring function according to any one of claims 2 to 7. The visible light coupler is
A reflector that reflects a portion of the light propagating in the output waveguide;
At least one monitoring waveguide that propagates the light reflected by the reflection unit and outputs the light to the at least one photodiode;
The light source with a monitoring function according to claim 1, further comprising: The at least one photodiode is configured to monitor the light output at the combining section or the output waveguide,
The light source with a monitoring function according to any one of claims 1 to 9, wherein output lights of the plurality of laser diodes are time-division modulated so that a frame rate is higher than 60 Hz. The at least one photodiode is configured to monitor the light output at the combining section or the output waveguide,
The output light of the plurality of laser diodes is frequency-modulated using a frequency which is a frequency of several hundred MHz to several GHz and which is different for each of the laser diodes outputting red light, blue light or green light. A light source with a monitoring function according to any one of claims 1 to 9.   A connection between the plurality of laser diodes and the plurality of input waveguides such that the at least one photodiode detects light which is emitted from the plurality of laser diodes and can not be connected to the plurality of input waveguides. The light source with a monitoring function according to claim 1, characterized in that the vicinity of the portion is arranged.

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